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K. Ozawa, Univ. of Tokyo, for the PHENIX collaboration

K. Ozawa, Univ. of Tokyo, for the PHENIX collaboration. Measurements of J/ y → e + e - in Au-Au collisions at √ s NN = 200 GeV. Unlike sign. Unlike sign. Like sign. Like sign. Flavor 4. J/ Y yield measurements. PHENIX EID detectors. J/ Y suppression as a QGP signal

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K. Ozawa, Univ. of Tokyo, for the PHENIX collaboration

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  1. K. Ozawa, Univ. of Tokyo, for the PHENIX collaboration Measurements of J/y → e+e-in Au-Au collisions at √sNN = 200 GeV Unlike sign Unlike sign Like sign Like sign Flavor 4 J/Y yield measurements PHENIX EID detectors • J/Y suppression as a QGP signal • T. Matsui and H. Satz, Phys. Lett. B178, 416 (1986) • Enhancement at RHIC Energy? • R.L. Thews : coalescence calculation • R. Rapp : recombination • Initial state effects? • Shadowing • Parton saturation • 49.3 M minimum bias Au-Au reactions are analyzed. • Momentum and charge sign • Drift Chamber • Pad Chamber • Electron identification • Ring Image Cherenkov (RICH) • Electromagnetic Cal. (EMC) Detector system RICH parameters • Distance between ring center and track projection (Disp) • Number of hit PMT in the region (NPMT) • Region: 3.4 cm < r < 8.4 cm • Numbers come from position resolution • Number of good timing hit PMT (NPMT-Timing) • Ring shape (S) • S = Si ((Ri – R0)2 * n.p.ei )/ Si n.p.ei • R0 = 5.9 cm (Expected ring radius) Need: Systematic study of J/Y yield Measurements in Au-Au, d-Au, p-p over wide kinematical range See other posters for d-AU, p-p and muon channel results. RICH ring Schematic view of RICH Analysis BdN/dy per binary collision The first result is already published. nucl-ex/0305030, accepted for P.R.C • Signal counting in 3.1 ± 0.3 GeV/c2 • Most likely value and 90% C.L. is calculated. All Charged particle • RICH cuts are applied. • Energy – Momentum matching is applied. • Background is evaluated by like-sign pair distribution. Apply RICH cut BG -4.1 Energy / Momentum -2.6 Unlike sign Like sign Subtracted • BdN/dy : 0-20% centrality 40-90 % central Ncoll = 45 20-40% 20-40 % central Ncoll = 296 -0.68 -0.54 0-20 % central Ncoll = 779 -0.97 -0.77 40-90% normal nuclear absorption BdN/dy(pp): 1.46±0.23±0.22±0.15 X 10-6 SPS NA50 normalizedto p+p point Invariant Mass (Minimum Bias) [GeV/c2] Invariant Mass [GeV/c2] BdN/dy per binary collision Another set of parameters Run4 expectation • Significantly larger data sets are required to address various models. • We have just started data acquisition in Run4. [1] [3] 0-20% 20-40% 40-90% [2] Invariant Mass for each centrality [GeV/c2] NPMT [1] R.L. Thews et al., Phys. Rev. C 63, 054905 (2001) [2] L. Grandchamp et al., Nucl. Phys. A709, 415 (2002) [3] A. Andronic et al., Phys. Lett. B571, 36 (2003) Invariant Mass (Minimum Bias) [GeV/c2] Significance of Run4 data is estimated. • Another set of cut parameters is applied for crosscheck. • Consistency between p+p and simulation is checked. • Results are consistent with paper results. • ∫Ldt (delivered) = 316 mb-1 for 14 weeks • 60% of PHENIX efficiency • 65% of vertex and quality assurance factor • ∫Ldt (recorded) = 123 mb-1 • Detector operation is improved (×4) Disp • 2.6 s significance is expected, even with strong suppression. p+p and Sim.

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